Controls for electrostatic spraying apparatus



Nov. 22, 1966 N. O. MIOTTEL CONTROLS FOR ELECTROSTATIC SPRAYING APPARATUS Filed June 22, 1964 AIR PRESSURE SOURCE Zfl /5 g y ELECTRIC ENERGY PANT SOURCE SOURCE I INVENTOR. BY 770;?22422 P/f/Ebii/ HTTORNEY United States Patent 3,286,977 CONTROLS FOR ELECTROSTATIC SPRAYING APPARATUS Norman 0. Miottel, Detroit, Mich., assignor to General Motors Corporation, Detroit, Micln, a corporation of Delaware Filed June 22, 1964, Ser. No. 377,004

5 Claims. (Cl. 25146) This invention relates to improvements in controls adapted for use, although not exclusively, with electrostatic spraying apparatus.

Because electrostatic spraying materials usually dry and congeal relatively quickly, the controls therefore can become clogged during normal operation. This is particularly a problem with valving that does not aflord rapid enough on and GE action.

Accordingly, a new and different control is proposed that affords a minimum response time for on and off action, that is easily assembled, and that provides an effective seal for isolating the spraying material.

More specifically stated, the invention comprehends the use of a control pressure for producing the on and off action with provision for obtaining fast response times. This provision additionally permits easy assembly and subsequent servicing while affording a very effective isolation of the control pressure from the spraying material.

The foregoing and other objects and advantages of the invention will be apparent from the following description and from the accompanying drawing in which the single figure portrays schematically a control incorporating the principles of the invention.

Referring now to the drawing in detail, the numeral denotes generally a control for an electrostatic spraying medium, such as paint or even wax, derived from a paint source 12 and supplied thereto by a suitable pump 14. The paint then is supplied to an appropriate spraying head 16 that provides the necessary acceleration for the paint. The head 16 is connected to a high potential electric energy source 18 and has a certain polarity, whereas the article to be painted has an opposite polarity. This arrangement creates the necessary intense electrostatic field for causing the charged particles emitted by the head 16 to be attracted to the oppositely charged article.

The control 10 includes a housing 20 provided with an input 22 and an output 24. Both the input 22 and the output 24 are joined respectively to the pump 14 and the head 16 by appropriate connectors and tubing. The housing lil has an annular wall or boss 26 defining a control chamber 28. The boss 26 is internally threaded and at the base or bottom thereof has a flat sealing surface 30 and at the external end a stop flange denoted generally as 32. The distance between sealing surface 30 and the stop flange 32 is carefully controlled for reasons to be explained. The sealing surface 30 surrounds a spherical valve seat 34 with which both the input 22 and the output 24 communicate.

The control of the communication between the input 22 and the output 24 is achieved by a fluid pressure, which is that derived from an air pressure source 36, and a flexible diaphragm 38 positioned on the sealing surface 30. The flexible diaphragm 38 is formed of some resilient material that will have the necessary flexing characteristics for enabling it to return to the illustrated normal position from a position in which a complete seal is established with respect to the valve seat 34 so that no I 3,286,977 Patented Nov. 22, 1966 communication is permitted between the input 22 and the output 24. Also, the flexible diaphragm 38 is made of a material that is not damaged by whatever spraying medium is employed.

In effect, the flexible diaphragm 38 establishes a transfer chamber 40 directly opposite the control chamber 28. The isolation of the paint in the transfer chamber 40 from the control chamber 28 is achieved by any known type of seal such as an O-ring 42 that presses against the top of the flexible diaphragm 38 at its periphery. The O-ring 42 is easily inserted into the control chamber 28 and is equally as easily removed for servicing purposes.

The provision for compressing the O-ring 42 and connecting the air pressure source 36 to the control chamber 28 is accomplished by a closure member, e.g., as a cap 44. The cap 44 is externally threaded to mate with the internally threaded boss 26 and is screwed downwardly as viewed until a shoulder 46 formed thereon engages the stop flange 32 on the boss 26. Then a seal or O-ring engaging surface 48 will have compressed the O-ring 42 the necessary amount to gain an effective seal between the control chamber 28 and the transfer chamber 40. This is achieved by controlling the dimensions between the shoulder 46 and the surface 48 on the cap 44 along with the dimension, as mentioned, between the seating surface 30 and the stop flange 32. Hence, during assembly, the cap 44 need only be turned until the shoulder 46 tightly engages the stop flange 32. At this time it is known that the O-ring 42 is compressed the necessary amount, thus in effect providing an automatic and convenient adjustment. This gives assurance that the O-ring 30 will not be undercompressed and permit a leak or overcompressed and possibly damaged.

The cap 44 further provides an inlet 50 that communicates with the air pressure source 36 via a manually operable valve 52 and a restricted exhaust passage that connects the inlet 50 to atmosphere. The type of valve 52 employed may be of any kind well known in the art that is manually and selectively operable to connect or disconnect the air pressure source 36 from the control chamber 38.

In operation with the manual valve 52 in its off position, v

the control chamber 28 is connected to the atmosphere via the inlet 50 and the exhaust passage 54. Consequently, the flexible diaphragm 38 will be in its normal position and the paint will be allowed to pass from the input '22 by way of the valve seat 34 and the transfer chamber 40 to the outlet 24 as soon as operation of the pump 14 is commenced. The spraying process will take place as previously briefly described.

If now for some reason it is necessary to cut off the supply of paint, the manually control valve 52 is moved to its open position and then air under pressure is transferred from the air pressure source 36 via the inlet 50 in the cap 44 to the control chamber 28. This air under pressure will force the flexible diaphragm 38 downwardly into sealing engagement with the valve seat 34 and stop the communication between the inlet 22 and the outlet 24 via the transfer chamber 40. The exhaust passage 54 will be continuously exhausting this air pressure but is of a calculated small area so as to present a restriction and therefore not permit the air pressure to be reduced below some amount less than that decided necessary to maintain the sealing relationship of the flexible diaphragm 38 relative to the valve seat 34.

When the supply of plaint is to be recommenced, the manually operable valve 52 is returned to its closed posi- I faulty operation.

3 tion stopping the supply of air pressure from the source 36 to the control chamber 28. Usually there would be a short time delay before the flexible diaphragm 38 returns to its illustrated normal position and permits full communication between the input 22 and the output Z4via the transfer chamber 40, but because of the exhaust passage 54, any residual pressure is quickly relieved to give an almost instantaneous return of the flexiblediaphragm38 to its normal position. This protects against the undesired drying or congealing of the paint to'the valve seal 34 during excessive time delays. Of course,

if this were permitted, clogging wouldoccur and then, Also, there is nothing, e.g., a positive stop, preventing the flexible diaphragm 38 from going slightly beyond its normal position and thus constituting a source of wear.

From the foregoing it will be appreciated that the control is one that is initially easily assembled without requiring any special techniques or instruction and that is also easily serviced in the field. The vitally necessary seal is achieved as a part of the assembly itself. .Moreover, the response time is instantaneous, i.e., the on and off action because of the provision for release' of the residual pressure. I

The invention is to be limited only by the following claims.

What is claimed is:

1. In a control valve for electrostatic spraying apparatus; the combination of a housing including an annular wall defining a control chamber, an external stop flange on the 'wall for establishing the external limit of the control chamber, a spherical valve seat, an annular sealing J surface surrounding the valve seat and positioned inwardly from the stop flange a certain distance for establishing the internal limit of the control chamber, and an input and an output both communicating with the valve'seat;

a flexible. annular diaphragm situated on the sealing surface; an O-ring positioned on the diaphragm proximate the periphery thereof; a cap internally threaded to they annular wall and including a shoulder for engaging the stop flange and an O-ring engaging surface arranged a predetermined distance fromthe shoulder'for compressing the O-ring a predetermined amount adequate to provide a sealing relationship with the flexible diaphragm, the cap including an inlet extending to the diaphragm and a restricted exhaust opening; a source of fluid pressure; and a manually controllable valve selectivity operative to connect the source to the inlet so as to cause the diaphragm to be biased from a normal position and against the valve seat for interrupting communication between the inlet and outlet and for disconnecting the source from the inlet so to permit the flexible diaphragm to return to the normal position and out of engagement with the valve seat for permitting communication between the input and output, the restricted exhaust opening facilitating the release of pressure in the control chamber when V t A}. l and deflect. the diaphragm between the inlet and outlet and for disconnecting the source from the inlet so to permit the flexible diaphragm permit communication between the input and the output,

.the housing having a stop a certain distance from the diaphragm, asealing element positioned against the flexible diaphragm, a connector secured to the housing and in engagement with the stop, the connector including a a sealing surface so arranged as to compress the sealing element a predetermined amount adequate to establish a sealing relation between the sealing element and the diaphragm when the connector is in engagement with the stop, the connector also including :an inlet and a 1 restricted exhaust opening, a'source of fluid pressure,

and manually controllable means for selectively con- I necting the source to the inlet so that pressure is-applied to the "diaphragm urging the diaphragm from a normal position and into engagement with the valve seat thereby interrupiting cornmunicationbetween the input and output and for disconnecting the source from the inlet so that the pressure is relieved by way of the restricted exhaust opening thereby permitting the diaphragm to return to the normal position.

4..In a control for electrostatic'spraying apparatus;

the combination of a housing including a stop, a control chamber and a transfer chamber, an input and an output both communicating with the transfer chamber, a flexible diaphragm interposed between the control and transfer chambers, a sealing element for effecting a sealing relation between the chambers, a closure member for the control chamber including an inlet and a restricted exhaust opening, the closure member being secured to the housing in a certain fixed position relative to thestop and also including a sealing surface so arranged as to compress the sealing element When the closure member;

is in the certain fixed position a predetermined amount adequate to produce the sealing relationship between the transfer and control chambers, 21 source of pressure fluid,

. manually controllable means selectively operative to conthe manually controllable valve disconnects the source from the control chamber.

2. In a control for electrostatic spraying apparatus; the combination of a housing including an annular wall defining a control chamber, an external stop flange on the wall for establishing the external limit of the control chamber, a spherical valve seat at the bottom of the control chamber, an annular sealing surface surrounding the valve seat and positioned inwardly from the stop flange a certain distance for establishing the internal limit of the control chamber, and an 'input and an output both communicating with the valve seat; a flexible annular, diaphragm situated on the sealing surface, a sealing element arranged on the flexible diaphragm; a closure member for closing the control chamber and including an inlet and a restricted exhaust opening; a source of fluid pressure communicating with the ,inlet; and manually controllable means for connecting the source to the inlet so that pressure fluid will be applied against the diaphragm nect the inlet to the source so as to cause pressure fluid to deflect the flexible diaphragm from a normal position to a closing position in which the communication between the input and output is interrupted and for disconnecting the inlet from the source to permit the pressure fluid to be relieved by way of the restricted exhaust opening andallow the flexible diaphragm to return to'the normal position.

5. A control for liquid spraying material utilized in electrostatic spraying apparatus, the combinationof a. 7

housing having a valve seat therein, an input and an output both communicating with the valve seat for transferring the liquid material therebetween, a flexible diaphragm mounted in the housing adjacent. the valve seat and deflectable from a normal'position to an engaged position relative to the valve seat so as to prevent communication between the input and the output, a source of control pressure for deflecting the diaphragm to the engaged position, a sealing element engageable with the flexible diaphragm and operative to prevent commingling of the liquid material and the control pressure, and means connecting the source of control pressure to the diaphragm; the connecting means including an exhaust opening and a sealing element engaging surface for compressing the sealing element a predetermined.

amount and manually operable means selectively operative to connect the source to the flexible diaphragm so as to from a normal position andv against the valve seat so as to interrupt communication 5 cause the flexible diaphragm to be deflected to the engaged position and thereby interrupt communication between the input and output and for disconnecting the source from the diaphragm so that the pressure acting on the diaphragm is relieved by way of the exhaust opening.

References Cited by the Examiner UNITED STATES PATENTS 859,152 7/1907 Tippett 25133 1,158,869 11/1915 Thomson 25146 2,63 8,243 5/1953 Davies. 3,083,943 4/1964 Stewart et a1. 251--331 X FOREIGN PATENTS 832,817 2/1952 Germany.

M. CARY NELSON, Primary Examiner.

ARNOLD ROSENTHAL, Examiner. 

1. A CONTROL FOR LIQUID SPRAYING MATERIAL UTILIZED IN ELECTROSTATIC SPRAYING APPARATUS, THE COMBINATIN OF A HOUSING HAVING A VALVE SEAT THEREIN, AN INPUT AND AN OUTPUT BOTH COMMUNICATING WITH THE VALVE SEAT FOR TRANSFERRING THE LIQUID MATERIAL THEREBETWEEN, A FLEXIBLE DIAPHRAGM MOUNTED IN THE HOUSING ADJACENT THE VALVE SEAT AND DEFLECTABLE FROM A NORMAL POSITION TO AN ENGAGED POSITION RELATIVE TO THE VALVE SEAT SO AS TO PREVENT COMMUNICATION BETWEEN THE INPUT AND THE OUTPUT, A SOURCE OF CONTROL PRESSURE FOR DEFLECTING THE DIAPHRAGM TO THE ENGAGED POSITION, A SEALING ELEMENT ENGAGEABLE WITH THE FLEXIBLE DIAPHRAGM AND OPERATIVE TO PREVENT COMMINGLING OF THE LIQUID MATERIAL AND THE CONTROL PRESSURE, AND MEANS CONNECTING THE SOURCE OF CONTROL PRESSURE TO THE DIAPHRAGM; THE CONNECTING MEANS INCLUDING AN EXHAUST OPENING AND A SEALING ELEMENT ENGAGING SURFACE FOR COMPRESSING THE SEALING ELEMENT A PREDETERMINED AMOUNT AND MANUALLY OPERABLE MEANS SELECTIVELY OPERATIVE TO CONNECT THE SOURCE TO THE FLEXIBLE DIAPHRAGM SO AS TO CAUSE THE FLEXIBLE DIAPHRAGM TO BE DEFLECTED TO THE ENGAGED POSITION AND THEREBY INTERRUPT COMMUNICATING BETWEEN THE INPUT AND OUTPUT AND FOR DISCONNECTING THE SOURCE FROM THE DIAPHRAGM SO THAT THE PRESSURE ACTING ON THE DIAPHRAGM IS RELIEVED BY WAY OF THE EXHAUST OPENING. 